Welcome to HVAC-Talk.com, a non-DIY site and the ultimate Source for HVAC Information & Knowledge Sharing for the industry professional! Here you can join over 150,000 HVAC Professionals & enthusiasts from around the world discussing all things related to HVAC/R. You are currently viewing as a NON-REGISTERED guest which gives you limited access to view discussions

To gain full access to our forums you must register; for a free account. As a registered Guest you will be able to:

Participate in over 40 different forums and search/browse from nearly 3 million posts.

jeff I don't know the % that have backup heat. I had it put in mine and when I saw how good the system worked I disconnected it. So for me it was a waste of money. The idea is to size your system for 9o to 95% of your heat need and the 5 to 10% that you might need every 3 or 4 years can be made up with backup that could save you several thousand dollars in the install. To me the big problem is that if you have a problem with your system You want know it until you get your power bill as the backup would make up the heat loss for say low freon. If it happens slowly you would get used to the higher power bills and never know that you had a problem. Also it is hard to burn down your house if you don't have any fireworks in your system. That's just my 2 cents. You will love Geothermal. Curtis

I routinely size the 2 stage geo systems so the first stage operation will handle most all the cooling and heating load with the second stage rarely being used. I will also configure the t'stat so there is no auxillary heat available, the t'stat would have to be manually set to "Emergency" heat in the event of a system shut down.

This allows for maximum energy/cost savings which is the very reason the homeowner has invested in such a system. I also size the loop field with an additional 20% capacity to allow the system to always work at it's maximum efficiency. I never want to receive a phone call from the customer saying the geo system is not performing as intended.

I'm installing a 5 and a 3 Tom Geo in a house and it's 7000 Sq ft. 3500 on main and 3500 in basement. I sized for the house to be 75 at 0 outside on heating and 70 when it's 100 on cooling. Allot depends on how your house is built. I also done a max water temp in summer or 95 and min winter of 35. This makes my loop longer to accept and reject heat. Soil matters too. I'm not installing backup cause it's not need until -3. And the homeowner oppt out of it. You can always install later. I don't see no cons to it. The pros are if your compressor goes out, you still have heat.

If you over size the heat pump you are going to be paying for a system larger than you need for 95% of the time. During the cooling season with an over sized system it will cool the house too quickly and not remove the humidity so it will feel calmy.

In our climate we have a greater heating load than cooling so I size a 2 stage unit for 95% of the heating load and provide some form of auxiliary or backup heat - either gas furnace or electric strip heat. A 2 stage unit allows for the 1st stage to nicely cover the cooling load without being grossly oversized. A single stage unit in my climate would be either (1) on backup all the time in heating or (2) cool very poorly (as in not be comfortable - you could probably hang meat in a house with a grossly oversized AC)